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How to test an IGBT

An Insulated Gate Bipolar Transistor (IGBT) is a three-terminal semiconductor used as a silent high-speed electronic switch; one terminal is the “Emitter,” the second is the “Collector” and the third is the “Gate.” These devices are ideally suited for modern equipment, such as variable speed refrigerators, stereo systems with switching amplifiers, electric cars, trains and many other single or three phase devices. With their ultra-low voltage requirement, IGBTs can range in size from a matchbox to a flat brick. Testing an IGBT is fairly straightforward.

Single Gate IGBT

Connect one terminal of a 12 volt lamp to the positive terminal of a 12 volt battery, and the other terminal to the collector terminal marked with the letter "C" on a single IGBT brick.

Connect the negative terminal of the 12 volt battery directly to the Emitter terminal marked with the letter "E" on the IGBT.

Test the “ON” sequence. First touch the positive terminal on the battery with one finger, and then touch the smaller terminal marked with the letter "G" for gate with the other finger. This will turn on the light.

Remove both fingers and the light should stay on. Be aware that the gate circuit is sensitive and you can destroy the IGBT if you reverse the order by touching the gate terminal before you touch the positive battery terminal. Note that since the static electricity conducted by your body is miniscule, you cannot feel it and it cannot harm you.

Test the “OFF” sequence. First touch the negative terminal on the battery with one finger, and then touch the gate terminal on the IGBT with another finger. The light should go out. Ensure you don't destroy the IGBT by touching the gate terminal before touching the negative terminal on the battery.

Dual Gate IGBT

Use the same test light as for the single gate test. Examine the dual IGBT terminals; you’ll notice that it has a single common emitter terminal, together with two collector terminals marked “C1” and “C2." In addition, there are two gate spade connectors on the upper side of the IGBT, one marked “G1” and the other marked “G2."

Connect the negative battery terminal to the common emitter terminal, and the positive lamp connector to the terminal marked “G1."

Test the “ON” sequence of the “G1” circuit: Touch the positive terminal on the battery, and then touch the “G1” spade connector. The light should switch on. Again, do not reverse the sequence.

Test the “OFF” sequence. Touch the negative terminal on the battery, and then touch the “G1” spade connector on the IGBT. The light should switch off.

Repeat this test by connecting the lamp to the “E2” terminal, and then test the ON/OFF sequence in turn via the “G2” terminal.

Tip

You can test multiple gate IGBTs by repeating the dual gate sequence. Connect the negative battery terminal to the common emitter terminal, and then test each C and G circuit on a multiple IGBT.

Whether you’re testing a single or multiple IGBT, if the lamp lights up as soon as you connect the IGBT to the battery, it means the “ON” circuit of that particular gate is already charged, so you can turn the light off and complete the test by first touching the negative battery terminal, and then touching the emitter terminal on the unit.

Things You'll Need

  • 12V battery
  • 12V lamp
  • Insulated wire
  • Connectors such as Alligator clamps
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About the Author

After graduating from the University of the Witwatersrand and qualifying as an aircraft engineer, Ian Kelly joined a Kitchen remodeling company and qualified as a Certified Kitchen Designer (CKD). Kelly then established an organization specializing in home improvement, including repair and maintenance of household appliances, garden equipment and lawn mowers.